Noise induced hearing loss

Noise induced hearing loss can occur over long exposure to loud noise or a one time exposure to a loud sound such as an explosion, this happens when damage occurs to the minute hair cells in the cochlear. These hair cells send different sound frequencies to the auditory nerve which enables us to identify them as different sounds, when these become damaged then the hearing is affected.

If you have excellent hearing then you will be able to hear a range of different sounds from 20Hz to 20,000 Hz but over a period of time the hair cells can become damaged and if the damage is due to loud noise it is usually the high frequency area of the cochlea which becomes affected.

How is sound measured?

Sound is measured in decibels which goes down past 0 dB although most people hear sounds only down to 0dB which is as quiet as the rustling sound of leaves, some people are known to hear sounds right down to -15dB. Sounds of 85dB and over can cause permanent damage to the hearing which results in hearing loss to some degree, the longer you are exposed to noises of this level or above it the more damage is caused and the hearing loss can be severe.

Some common sounds measured in decibels

Some sounds are louder in decibels than what you might think and noise induced hearing loss is perhaps one of the most common types of hearing loss that people face today. This is due to workers in large industrial plants wearing inadequate ear protection day in day out, a recent study showed that over 40 million people are exposed everyday in the workplace to potentially harmful noise.

• A typical conversation will be around 60dB.
• A bulldozer in idle mode is around 85dB – this could potentially cause hearing loss after only one day at work without adequate ear protection.
• Music played on headphones at a typical volume level of 5 will be around 100Db – this could affect the hearing if played for 15 minutes per day.
• A sudden clap of thunder from a storm can reach 120dB which can cause some damage immediately.

Recommended guidelines for exposure to continuous loud noise is as follow

• 85dB – not more than 8 hours.
• 88 dB – not more than 4 hours.
• 91 dB – not more than 2 hours.
• 94 dB – not more than 1 hour.
• 97 dB – not more than 30 minutes.
• 100 dB – not more than 15 minutes.
• 103 dB – not more than 7 ½ minutes.
• 106 dB – not more than 4 minutes.
• 109 dB – not more than 2 minutes.
• 112 dB – not more than 1 minute.
• 115 dB – not more than 30 seconds.